1. Field of the Invention
This invention relates to mirrors such as are installed on bathroom walls, and more particularly to a mirror heated convectively and radiatively to a temperature exceeding ambient temperature to prevent fogging when water vapor is in the air.
2. Description of the Related Art
Devices for electrically heating and thereby defogging mirrors in warm and humid environments such as bathrooms have been disclosed in many patents. U.S. Pat. No. 4,665,304 to A. G. Spencer provides an extensive survey of the U.S. patent literature up to 1984. More recent U.S. patents disclosing heated mirrors are U.S. Pat. No. 4,940,317 to R. Reuben, U.S. Pat. No. 5,155,334 to J. A. Marstiller et al., U.S. Pat. No. 5,302,809 to A. Ghiassy, U.S. Pat. No. 5,380,981 to B. Feldman et al., U.S. Pat. No. 5,406,049 to C. Reiser et al., U.S. Pat. No. 5,731,569 to G. Crescenzo, U.S. Pat. No. 5,821,501 to H. Zorn, U.S. Pat. No. 5,904,874 to J. Winter, and U.S. Pat. No. 6,198,073 B1 to F. Gonzalez.
Electrical heating of a mirror is accomplished in all these references by a device rigidly attached to or otherwise in good thermal contact with the mirror so that heating occurs by conduction. In contrast, my U.S. Pat. No. 6,365,876 B1 discloses a wall-mounted cabinet having a pivotable door with opposed exterior and interior mirrors which are convectively and radiatively heated by a sheet heater disposed between the two mirrors and separated from each mirror by an air gap. The present invention uses the same technique to heat a single wall-mounted mirror.
Self-heated rear view mirrors for automotive vehicles such as cars and trucks are also known. GB1414905 to R. G. Gray discloses a mirror assembly having a mirror glass and a cover glass spaced apart by a peripheral seal to form a cavity between the two glasses which is filled with an inert gas. An electrical heating element is mounted in the cavity for demisting the glasses. The heating element is in the form of a coiled filament adjacent to the lower edge of the glasses. U.S. Pat. No. 2,797,287 to P. E. Prutzman discloses mirror assemblies, particularly for trucks, incorporating two resistance-wire coils mounted on a stiff asbestos board. Because the coils are in the major lower portion of the mirror casing, that portion is heated primarily by radiant heat while the casing upper portion is heated primarily by convection and conduction.
In view of the limitations of the related art, it is an object of the present invention to provide a wall-mounted mirror which can be defogged by a sheet heater separated from the mirror by an air gap.
Another object of the invention is to provide a mirror assembly which is protected against electrical shock.
A further object of the invention is to provide a mirror assembly that can be easily manufactured using high quality components.
Yet another object of the invention is to provide a mirror which can be reliably defogged in a warm, humid environment.
Other objects of the invention will become evident when the following description is considered with the accompanying drawing figures. In the figures and description, numerals indicate the various features of the invention, like numerals referring to like features throughout both the drawings and description.
These and other objects are achieved by the present invention which provides a wall-mounted mirror assembly including a frame having parallel top and bottom portions and parallel left and right portions orthogonal to the top and bottom portions, the four portions determining a rectangular aperture. The assembly further includes a mirror having parallel exterior and interior surfaces bounded by top, left, bottom and right edges coated with a layer of electrically non-conductive material. The bottom edge is closely received within and attached to a J-shaped metallic sheeting, and the interior surface is circumferentially attached to the four frame portions. The assembly further includes a rectangular sheet heater including a blanket with opposed electrically non-conductive first and second surfaces, and a bottom edge proximate to which are attached two electrical terminals. The blanket first surface is separated by an air gap from the mirror interior surface.